Nathaniel Corwin

Inorganic nitrogen removal in a combined tertiary treatment—marine aquaculture system—I. Removal efficiences

Abstract The increasing awareness that nitrogen is often a key nutrient controlling algal growth in coastal marine waters has led to a concerted effort to find ways to remove ammonia and nitrate from wastewaters. A novel approach to this problem involves the combining of algal and seaweed nutrient stripping processes with a marine aquaculture. Not only is nitrogen removed from wastewater, but important commercial shellfish and seaweeds are produced. A prototype process consisting of growth systems for marine algae, oysters and seaweed, joined in series, was fed secondarily treated wastewater, diluted 1:4 with seawater, for 11 weeks during the Summer of 1972. During this time 95 per cent of the influent inorganic nitrogen was removed by algal assimilation. The oysters in turn removed 85 per cent of the algae, but regenerated as soluble ammonia 16–18 per cent of the nitrogen originally bound in the algal cells. All of the regenerated nitrogen was removed in the seaweed system so that the total inorganic nitrogen removal efficiency of the system was 95 per cent. Phosphorus removal on the other hand was not nearly as complete as only 45–60 per cent was removed. The process has the capability of being expanded to include additional trophic levels in an integrated and highly controlled food chain system to serve the dual function of tertiary wastewater treatment and waste recycling through the production of shellfish and seaweeds.

The significance of organic phosphorus determinations in ocean waters

Abstract 1. 1. Total phosphorus can be measured by the Harvey method with an accuracy of about ± 5% (Standard deviation). The blank obtained using reagent grade chemicals without special purification is about 0·2 μgA/L. 2. 2. Organic phosphorus is determined by the difference between the inorganic and the total phosphorus concentrations. Unless this difference exceeds 10% of the concentration it cannot be considered significant. 3. 3. Analysis of almost a thousand samples from the equatorial Atlantic Ocean on which both inorganic and total dissolved phosphorus were determined indicates: 3.1. (a) that 95% of the surface water samples contain significant amounts of dissolved organic phosphorus. 3.2. (b) that the frequency of samples showing significant amounts of dissolved organic phosphorus decreases with depth and with the content of inorganic phosphorus. 3.3. (c) that at depths greater than 1,000 metres no measurable amounts of dissolved organic phosphorus are detectable by the present methods.

The temperature correction of oceanic inorganic phosphorus analyses

Abstract The colour intensity of the molybdate-blue complex in the analysis for inorganic phosphorus in sea-water increases 1·25 per cent per degree centigrade. The apparent phosphorus content of sea-water samples analysed in tropical regions may be erroneously high unless temperature is controlled or corrections are made. The effect of temperature correction on the agreement between total and inorganic phosphorus contents of Atlantic Ocean water is described. It is recommended that temperature corrections be included in future publications of data on the distributions of inorganic phosphorus.